Cost-benefit-analysis of coastal adaptation strategies and pathways. A case study in West Africa

Abstract

Understanding the level of vulnerability of human and natural systems to climate variability and change, and how investing in adaptive capacity now will prevent losing billions of dollars in damages in the future are pivotal to making decisions and developing policies related to coastal adaptation. The research presented in this paper focuses on developing a methodological framework to perform a cost-benefit-analysis of disaster risk reduction and climate change adaptation strategies (i.e., protect, accommodate, or retreat options). The method is tested in pilot-site case-studies along the West African countries of Ivory Coast, Ghana, Togo, and Benin. The criterion used in the cost-benefit analysis is the Net Present Value (NPV) for the different risk management alternatives, according to different time horizons and dynamic adaptation pathways to 2100, discount rates and low- and high-cost estimates. Overall, the research makes evident that coastal protection investment costs ensuring the lowest residual risk (virtually zero risk) to 2100 are so high that they are unlikely to be paid back by avoided damages. Planned retreat (coastal setbacks and/or accommodation) allows to obtain most of the benefits (50%–98%) at a fraction of the protection costs (2%–12%). Furthermore, the research provides strong evidence that, when coastal risks are dominated by frequent coastal floods (10-year return period), the cost recovery period for climate-proofing of buildings is low (a few decades) compared to protect or setback measures. Finally, the research illustrates that disaster risk reduction and climate change adaptation strategies cannot be examined in general, but that location specific analysis of both costs and benefits is required.